Simulated 21st century's increase in oceanic suboxia by CO<sub>2</sub>‐enhanced biotic carbon export

Oschlies, Andreas; Schulz, Kai G.; Riebesell, Ulf; Schmittner, Andreas

doi:10.1029/2007gb003147

Cited by 259 publications

(285 citation statements)

References 39 publications

(56 reference statements)

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“…Hence, it appears too early to make a judgement on the sensitivity and longevity of this feedback. If there is a significant enhancement in the C:N drawdown at the surface that translates into an enhanced carbon export, it will lead to higher oxygen consumption and a possible expansion of oxygen-minimum zones (73), linking to the oxygen-related feedback described in Responses to Ocean Warming and Acidification. ⅐ Increased production of extracellular organic matter under high CO 2 levels (51) may enhance the formation of particle aggregates (74,75) and thereby increase the vertical flux of organic matter (negative feedback) (76).…”

Section: Impacts On the Biological Carbon Pumpsmentioning

confidence: 99%

Sensitivities of marine carbon fluxes to ocean change

Riebesell

Körtzinger

Oschlies

2009

Proc. Natl. Acad. Sci. U.S.A.

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273

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Throughout Earth's history, the oceans have played a dominant role in the climate system through the storage and transport of heat and the exchange of water and climate-relevant gases with the atmosphere. The ocean's heat capacity is Ϸ1,000 times larger than that of the atmosphere, its content of reactive carbon more than 60 times larger. Through a variety of physical, chemical, and biological processes, the ocean acts as a driver of climate variability on time scales ranging from seasonal to interannual to decadal to glacial-interglacial. The same processes will also be involved in future responses of the ocean to global change. Here we assess the responses of the seawater carbonate system and of the ocean's physical and biological carbon pumps to (i) ocean warming and the associated changes in vertical mixing and overturning circulation, and (ii) ocean acidification and carbonation. Our analysis underscores that many of these responses have the potential for significant feedback to the climate system. Because several of the underlying processes are interlinked and nonlinear, the sign and magnitude of the ocean's carbon cycle feedback to climate change is yet unknown. Understanding these processes and their sensitivities to global change will be crucial to our ability to project future climate change.climate change ͉ marine carbon cycle ͉ ocean acidification ͉ ocean warming T he ocean is presently undergoing major changes. Over the past 50 years, the ocean has stored 20 times more heat than the atmosphere (1). The Arctic Ocean surface layers have recently experienced a pronounced freshening (2), and although there is still considerable uncertainty in current observational estimates (3), climate models run under increasing atmospheric CO 2 levels essentially all predict a slowdown of the Atlantic meridional overturning circulation (MOC), which is part of the global thermohaline circulation (4). Since preindustrial times, the ocean has also taken up Ϸ50% of fossil fuel CO 2 , which has already led to substantial changes in its chemical properties (5).Carbon fluxes from the sea surface into the ocean interior are often described in terms of a solubility pump and a biological pump (6). The abiotic solubility pump is caused by the solubility of CO 2 increasing with decreasing temperature. In present climate conditions, deep water forms at high latitudes. As a result, volume-averaged ocean temperatures are lower than average sea-surface temperatures. The solubility pump then ensures that, associated with the mean vertical temperature gradient, there is a vertical gradient of dissolved inorganic carbon (DIC). This solubility-driven gradient explains Ϸ30-40% of today's ocean surfaceto-depth DIC gradient (7).A key process responsible for the remaining two thirds of the surface-to-depth DIC gradient is the biological carbon pump. It transports photosynthetically fixed organic carbon from the sunlit surface layer to the deep ocean. Integrated over the global ocean, the biotically mediated oceanic surface-to-depth DIC grad...

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Section: Impacts On the Biological Carbon Pumpsmentioning

confidence: 99%

Sensitivities of marine carbon fluxes to ocean change

Riebesell

Körtzinger

Oschlies

2009

Proc. Natl. Acad. Sci. U.S.A.

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273

199

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“…The UVIC2-8 model is the University of Victoria (UVic) Earth System Climate Model (Weaver et al, 2001) in the Redfield stoichiometry configuration described by Oschlies et al (2008). The oceanic component is a fully threedimensional primitive-equation model with nineteen levels in the vertical, ranging from 50 m thickness near the surface to 500 m in the deep ocean.…”

Section: A7 Uvic2-8mentioning

confidence: 99%

Oxygen and indicators of stress for marine life in multi-model global warming projections

et al. 2013

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Decadal-to-century scale trends for a range of marine environmental variables in the upper mesopelagic layer (UML, 100–600 m) are investigated using results from seven Earth System Models forced by a high greenhouse gas emission scenario. The models as a class represent the observation-based distribution of oxygen (O2) and carbon dioxide (CO2), albeit major mismatches between observation-based and simulated values remain for individual models. By year 2100 all models project an increase in SST between 2 °C and 3 °C, and a decrease in the pH and in the saturation state of water with respect to calcium carbonate minerals in the UML. A decrease in the total ocean inventory of dissolved oxygen by 2% to 4% is projected by the range of models. Projected O2 changes in the UML show a complex pattern with both increasing and decreasing trends reflecting the subtle balance of different competing factors such as circulation, production, remineralization, and temperature changes. Projected changes in the total volume of hypoxic and suboxic waters remain relatively small in all models. A widespread increase of CO2 in the UML is projected. The median of the CO2 distribution between 100 and 600m shifts from 0.1–0.2 mol m−3 in year 1990 to 0.2–0.4 mol m−3 in year 2100, primarily as a result of the invasion of anthropogenic carbon from the atmosphere. The co-occurrence of changes in a range of environmental variables indicates the need to further investigate their synergistic impacts on marine ecosystems and Earth System feedbacks

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“…The authors attributed these changes to an increase in carbon overconsumption in the dominant phytoplankton groups and outlined the possibility of a more efficient carbon pump under future ocean conditions once this carbon-enriched POM sinks out of the surface ocean. Using a global biogeochemical model, Oschlies et al (2008) extrapolated these findings to the global ocean and found that the enhanced carbon export may lead to an expansion in suboxic water volume by up to 50% until the end of this century.…”

Section: Introductionmentioning

confidence: 99%

Ocean Acidification-Induced Restructuring of the Plankton Food Web Can Influence the Degradation of Sinking Particles

et al. 2018

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Ocean acidification (OA) is expected to alter plankton community structure in the future ocean. This, in turn, could change the composition of sinking organic matter and the efficiency of the biological carbon pump. So far, most OA experiments involving entire plankton communities have been conducted in meso-to eutrophic environments. However, recent studies suggest that OA effects may be more pronounced during prolonged periods of nutrient limitation. In this study, we investigated how OA-induced changes in low-nutrient adapted plankton communities of the subtropical North Atlantic Ocean may affect particulate organic matter (POM) standing stocks, POM fluxes, and POM stoichiometry. More specifically, we compared the elemental composition of POM suspended in the water column to the corresponding sinking material collected in sediment traps. Three weeks into the experiment, we simulated a natural upwelling event by adding nutrient-rich deep-water to all mesocosms, which induced a diatom-dominated phytoplankton bloom. Our results show that POM was more efficiently retained in the water column in the highest CO 2 treatment levels (>800 µatm pCO 2 ) subsequent to this bloom. We further observed significantly lower C:N and C:P ratios in post-bloom sedimented POM in the highest CO 2 treatments, suggesting that degradation processes were less pronounced. This trend is most likely explained by differences in micro-and mesozooplankton abundance during the bloom and postbloom phase. Overall, this study shows that OA can indirectly alter POM fluxes and stoichiometry in subtropical environments through changes in plankton community structure.

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Simulated 21st century's increase in oceanic suboxia by CO₂‐enhanced biotic carbon export

Cited by 259 publications

References 39 publications

Sensitivities of marine carbon fluxes to ocean change

Sensitivities of marine carbon fluxes to ocean change

Oxygen and indicators of stress for marine life in multi-model global warming projections

Ocean Acidification-Induced Restructuring of the Plankton Food Web Can Influence the Degradation of Sinking Particles

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Simulated 21st century's increase in oceanic suboxia by CO2‐enhanced biotic carbon export

Cited by 259 publications

References 39 publications

Sensitivities of marine carbon fluxes to ocean change

Sensitivities of marine carbon fluxes to ocean change

Oxygen and indicators of stress for marine life in multi-model global warming projections

Ocean Acidification-Induced Restructuring of the Plankton Food Web Can Influence the Degradation of Sinking Particles

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Simulated 21st century's increase in oceanic suboxia by CO₂‐enhanced biotic carbon export